The firm, based in Grosvenor Gardens, close to London’s upmarket Belgravia area, says it “draws on extensive experience at boardroom level in government, multilateral diplomacy and international business to develop bespoke solutions for clients”.

“Our tailored approach means the directors are closely involved in the execution and detail of every project, supported by an in-house team of experienced investigators and professional intelligence analysts,” it says.

Mr Burrows formerly worked for the Foreign and Commonwealth Office as a counsellor, according to his LinedkIn profile, with postings to Brussels and Delhi in the early 2000s.

The dossier has been circulating in Washington for some time as media organisations, uncertain of its credibility, held back from publication.

Both Mr Trump and US president Barack Obama had been briefed on its contents and M r Trump has suggested American intelligence agencies may be responsible for its release.

In a press conference in New York on Wednesday that was dramatic and at times ill-tempered, the president-elect branded the dossier “fake news” and said it would be a “tremendous blot” on the agencies’ reputations if they were shown to have leaked it.

In the hours before his appearance, Mr Trump issued a series of tweets in which he denounced the document as “A COMPLETE AND TOTAL FABRICATION, UTTER NONSENSE”.

“Intelligence agencies should never have allowed this fake news to ‘leak’ into the public. One last shot at me. Are we living in Nazi Germany?” he tweeted.

Russian president Vladimir Putin’s spokesman Dmitry Peskov said the reports were “complete fabrication and utter nonsense” and the Russian government “does not engage in collecting compromising material”.

Standing in front of a row of US flags, Mr Trump blamed the creation of the dossier on his political opponents, who he said had “got together – sick people – and they put that crap together”.

Some of the more lurid details of the allegations were highly improbable because he was a “germophobe” who hated uncleanliness, he said, adding that he was very aware of the danger that hotel rooms may contain hidden cameras.

He thanked media organisations which declined to publish the “phoney stuff”, saying: “They looked at that nonsense that was released by maybe the intelligence agencies – who knows, but maybe the intelligence agencies – which would be a tremendous blot on their record if they in fact did that, a tremendous blot.

“A thing like that should never have been written, it should never have been had and it should certainly never have been released.”

Mr Trump insisted Moscow had “no leverage” over him as he had “no deals, no loans, no nothing” with Russia.